Modern data acquisition systems employ analog digital converters of essentially three types: Converters with very short conversion times, so-called half-flash converters; converters which operate according to the successive approximation (SAR) method, where the input voltage is compared to the output voltage of a digital-analog converter, which is controlled by the SAR register; and integrating converters, which are applied wherever short conversion times are not required. In the case of the so-called half-flash converter, the internal resistance must be small in order to keep error to a minimum. With regard to their input voltage, the SAR converters are very sensitive. As far as internal resistance is concerned, the most insensitive of all three types of converters in any case is the integrating converter. However, with this type of converter, one must be aware of the fact that the input current is essentially a leakage current and that when several integration levels are involved, the errors add up.